Study Of Priority Effects During Microbial Community Coalescence

The order and timing of species arriving at an ecological community will affect species interactions during community assembly,thus influencing the structure and function of the ecological community,namely,the priority effect.The mechanism is that the early arriving species can preempt or modify the existing ecological niche,thus affecting the successful colonization of the late arriving species.At present,most studies have focused on the priority effects of two or more known species,and few have studied the priority effects at the microbial community level.In this study,two soil microbial communities(A and B)were inoculated into the same sterilized soil in different order,and microbial community were analyzed by using 16 S r RNA genes high-throughput sequencing technology.Our objective is to learn how microorganisms response to priority effects and influencing factors,and analyze the role of priority effects in the plant root during microbial community coalescence.The main results are as follows:(1)Regardless of inoculation order,the results showed that the fewer ASVs were lost for early arriving microbial community than the late arriving community during community coalescence after three weeks of incubation.Pco A analysis showed that the Bray-Curtis dissimilarities was smaller between the coalescent community and the early arriving community than that of late arriving community.The Source Tracker analysis based on Bayesian algorithm showed that the proportion of the coalescence communities originated from the early arriving communities was higher than that from the late arriving communities.Clustering analysis showed that the coalescent community clustered with the early arriving community,while the late arriving community clustered alone.These results indicated that the priority effect had an influence on consequence of community coalescence.The fewer ASVs were lost for early arriving community than that the late arriving community after six weeks of incubation,but the difference of the number of lost ASVs was smaller than that of the third week.There was no significant difference between the distance of coalescent community and early arriving community and that of late arriving community.The proportion of species from the early arrival community was similar to that from the late arrival community.In conclusion,the influence of priority effects on consequence of community coalescence decreased with the incubation time.(2)Regardless of inoculation order,the results showed that after three weeks of incubation,the difference between the number of ASVs lost in the late arriving community and that in the early arriving community was greater than that in the 2 weeks interval.The difference of the Bray-Curtis dissimilarities was larger between the coalescent community and early arriving community than that of late arriving community.These results indicated that the longer the dispersal timing,the stronger the priority effects.The above differences were not significant after six weeks of incubation.It can be seen that with the extension of incubation time,the influence of dispersal timing on the strength of priority effect weakened,but the influence of inoculation ratio did not have an obvious rule.(3)By comparing the co-occurrence networks between the coalescent and non-coalescent communities(incubated separately),it was found that the proportion of positive network connections was always higher and the modularization index was lower in most coalescent communities than in the non-coalescent communities.Firmicutes had higher niche overlap with other phyla in the coalescent community than in the non-coalescent community.The addition of late arriving community increased the diversity of coalescent community in a short period of time.Compared with the similar nutritional condition of non-coalescent community,the competition between species increased,some relatively weak competitive species are excluded,thus the competition between species is slower.There are more positive correlations than non-coalescent communities,which tend to co-occur and are less divided into modules.At the same time,late arriving communities increased competition among species with similar ecological niches.(4)During the microbial community coalescence in plant root,the Bray-Curtis dissimilarities was smaller between the coalescent community and the early arriving community than that of late arriving community.Regardless of the inoculation order,at the family level,clustering analysis showed that the coalescent community always clustered with early arriving community,and the late arriving community clustered alone.These results indicate that the priority effect has an influence on consequence of community coalescence.In conclusion,we indicated that the role of priority effects during microbial community coalescence in soil and plant root,and revealed microbial community in responsing to priority effects.